#include <condition_variable>
#include <mutex>
#include <future>
#include <thread>
#include <iostream>
#include <queue>

std::queue<int> queue;
std::mutex queueMutex;

std::condition_variable queueCondVar;

void provider(int val)
{
	// push different values (val til val+5 with timeouts of val milliseconds into the queue
	for (int i = 0; i < 6; ++i) {
		{
			std::lock_guard<std::mutex> lg(queueMutex);
			queue.push(val + i);
		} // release lock
		queueCondVar.notify_one();
		std::this_thread::sleep_for(std::chrono::milliseconds(val));
	}
}
void consumer(int num)
{
	// pop values if available (num identifies the consumer)
	while (true) {
		int val;
		{
			std::unique_lock<std::mutex> ul(queueMutex);
			queueCondVar.wait(ul, [] { return !queue.empty(); });
			val = queue.front();
			queue.pop();
		} // release lock
		std::cout << "consumer " << num << ": " << val << std::endl;
	}
}
int main()
{
	// start three providers for values 100+, 300+, and 500+
	auto p1 = std::async(std::launch::async, provider, 100);
	auto p2 = std::async(std::launch::async, provider, 300);
	auto p3 = std::async(std::launch::async, provider, 500);
	// start two consumers printing the values
	auto c1 = std::async(std::launch::async, consumer, 1);
	auto c2 = std::async(std::launch::async, consumer, 2);
}


